This invention is concerned with an apparatus for use in monitoring the closing action of a mould of a glassware forming machine in a cyclic process of forming glassware.
In the manufacture of glassware by the conventional process using an individual section machine, a gob of molten glass is first formed into a parison by either pressing or blowing in a blank (or parison-forming) mould at one station of the machine. Subsequently, the parison is blown into the final shape of the desired article of glassware in a blow mould at another station of the machine as a result of the application of air under pressure to the inside of the parison. Both these moulds are formed from mould portions which are separated to permit removal of a parison or article of glassware and are brought together again into a closed position of the mould for the formation of the next parison or article.
In this process, difficulties arise from time to time due to breakage of a parison in the blank mould and/or breakage of a parison or an article of glassware in the blow mould. When there is a breakage of either the parison or the article as aforesaid, a residue of broken glass (known as "cullet") may be left in the mould and the cullet can prevent formation of a satisfactory parison or article of glassware in the succeeding cycle of operation of the machine by preventing correct closure of the mould. Unless the presence of such cullet in either the blank mould or the blow mould is quickly detected by the operator of the machine and appropriate action taken to prevent several further cycles of the machine taking place, the presence of the cooled, and therefore hard, cullet in the mould can lead to serious damage to either of the moulds when their closing mechanisms, which generate very considerable forces, attempt to close the moulds. The result is that the machine may be put out of operation for a considerable period until replacement of the damaged mould can be undertaken. There is thus a loss of manufacturing time while the moulds are replaced and the replacement moulds are brought up to the correct working temperature.
It is desirable therefore to provide some means by which the malfunction leading to breakage in formation of cullet impeding the closing of either the blank mould or the blow mould is immediately detected and action taken to prevent more than one further cycle of operation taking place in at least that mould where the malfunction has occurred.
In European Patent Specification No. 59576, there is described a method and apparatus of monitoring the closing action of a mould in which a signal representative of the position of a part of the mould at the time when the mould should be closed is compared with a signal representative of the correct closed position of the mould. The position which is representative of the correct closed position of the mould is produced by averaging a selected number of the immediately preceding signals representative of the position of the part of the mould at the time when the mould should be closed. While the method and apparatus described in the aforementioned European Patent Specification represents a considerable advance over relying upon an operator of the machine to observe the consequences of a malfunction, the method and apparatus depends on averaging a predetermined number of signals and is hence incapable of detecting a further malfunction occurring on the first cycle of operation of the machine after the machine has been stopped because of a malfunction. Such a further malfunction may occur if the cullet has been incompletely cleared from the mould. Furthermore, the aforementioned method and apparatus requires relatively complex electronic equipment capable of synchronising a position signal with a time signal and storing a large number of successive signals.
It is an object of the present invention to provide an apparatus for use in monitoring the closing action of a mould of a glassware forming machine in which the above mentioned disadvantages are avoided.